Thermally adjustable electrical device enclosed within envelopes



April 8, 1952 ATHERTON 2,591,907

THERMALLY ADJUSTABLE ELECTRICAL DEVICE ENCLOSED WITHIN ENVELOPES Filed April 26, 1946 I i i w a Jzorzf INVENTOR ig/ Man ATTORNEY Patented Apr. 8, 1952 UNITED STATES PATENT OFFICE I THERMALLY ADJUSTABLE ELECTRICAL DE- VICE ENCLOSED WITHIN ENVELOPES Albert Horace Atherton, Ealing, London, England,

assignor to Electric & Musical Industries Limited, Hayes, England, a company of Great Britain Application April 26, 1946, Serial No. 665,032

In Great Britain February 27, 1945 Section 1, Public Law 690, August 8, 1946 Patent expires February 27, 1965 plicable is an electron discharge device employ- ,ing a hollow resonator. an electron beam which is caused to pass through the resonator and such devices must therefore Such devices employ be enclosed within an envelope which is evacuated or gas-filled. It is often required in such. devices to adjust the tuning of the hollow resonator and this operation is frequently performed by deforming or displacing a wall of the resonator. Whilst many proposals have, been made for adjusting the wall of the resonator from the exterior of the envelope, such proposals usually involve the use of metallic bellows attached to the envelope so that a mechanical force from the exterior of the envelope can be communicated to the wall of the resonator to 12 Claims.

enable the position of the wall to be changed.

Another example of an electrical device in which it may be required to adjust the position of an element enclosed within an envelope is an electrical condenser contained within an envelope wherein, in order to adjust the capacity of the" condenser, one electrode is required to be moved relatively to another electrode of the condenser from the exterior of the envelope. Since all parts of the devices which pass through the envelope have to be sealed in a gas-tight manner to the envelope, it is not readily possible to adjust the position of elements within the envelope unless recourse be had to the use of metallic bellows, which gives rise to practical difliculties.

parting movement to a wall thereof by thermal means. For example, it has been suggested to On'the other hand, in electron dis-* 1 charge devices, employing hollow resonators it has been suggested to tune the resonator by imheat and expand a rod connected to the wall of the resonator or to heat a bowed element connected to a rod in turn connected to the wall of the resonator. These prior. proposals, however, suffer from the disadvantagethat"whilst it is possible to obtain adjustment ofthe wall when causing expansion of the rod orbowed element, the rate of adjustment in the opposite direction is ,limited by the rate of cooling of the rod or bowed element. Furthermore; the operat ing temperature must be high to give a-reascnable rate of cooling so that the operatingposition of the wall must be at some distance from its position when-the rod or bowed element is cold and it is found, in practice, that thisdistance is perhaps two or three times the distance over which the tuning element is required to move for a desired tuning range. v

The object of the present inventionis to provide an electrical device enclosed within an envelope and having improved means for effecting adjustment of an element within theenvelope thermally, but in which the disadvantages mentioned above with the previously proposed thermal means are. reduced or overcome.

, According to one feature of the invention there is provided an electrical device enclosed within an envelope and having an element in said envelope which requires to be'adjusted, wherein thermal means are provided for adjusting the vposition of said element, said thermal means comprising at least two expansible members and means for individually heating said-members, said members being coupled to the. element requiring adjustment and being so arranged that when one of said members expands itcauses movement of said elementin one di- 3 rection and when theother. of said members expands it causes movement of the said element in the opposite direction whereby movement-of element in either direction can be efiected..,on differentially heating 'said members. With such a construction .it will be appreciated that a change in the position of the elementrequiring adjustment can be effected in either direction by, heating oneot said members more than the other, thus obviating the necessity of allowing cooling to occur before adjustmentin one direction can occurl Furthermore, the position of the element requiring adjustment need not be changedwhen raising said membersito their operating temperatures since substantially nochange in the position. of said element occurs .until differential heating of said jmemhers is efi'ected, with the result that the positibii of the element requiring adjustment with said rnembers cold can be substantially the same as its positionpwith said members equally hot; The invention. is particularly applicableto the tuning of hollowresonators employed in velocity-modulated jelectron discharge devices but is equally applicable for use in other electrical devices where it is not readilypossible' adjust the position of an element owing to e presence of an envelope. 7

In one form of the invention said expansible members are heated by electron bombardment and in such a case one or more cathodes are proprovided disposed in proximity to said expansible members, control of the electrons to cause heating of said members to the desired extent being effected by the provision of control electrodes which are suitably arranged and to which potentials can be applied to control the number of electrons permitted to bombard said expansible members.

In order that the said invention may be clearly understood and readily carried into effect, it will now be more fully described with reference to the accompanying drawings which illustrate the invention as applied to an electron discharge device employing a hollow resonator and in which:

Fig. 1 illustrates diagrammatically in longitudinal section an electron discharge device employing a hollow resonator, tuning of which is effected by thermal means constructed in accordance with one embodiment of the invention,

Figure 1a is a detail plan view of a part of the device shown in Figure 1, and Figure 2 is-a diagrammatic view illustrating thermal means constructed according to another embodiment of the invention.

As shown in Figure 1 of the drawing, the reference numeral I indicates in cross-section a hollow 'i'esonator of a velocity-modulated electron discharge device, said resonator being arranged within an evacuated envelope 2. Disposed in proximity to the resonator I is a cathode 3 arranged within a cathode shield 4. The resonator I is supported by a plurality of support rods two of which are shown in the drawing, the cathode 3 and shield 4 being carried by an insulating disc 6 also carried by the support rods 51 The support rods 5 and the elements carried thereby are in turn supported from the base or pinch I of the envelope 2 by support rods 8, one of which is shown in Figure 1. The device shown in the drawing is intended as a generator ofself-maintained oscillations and the resonator I is provided with an acceleration grid 9 and a pair of grids I0, electrons emanating from the cathode 3 being accelerated by the grid 9 and caused to pass through the grids Ill where the electrons become velocity-modulated, the electrons then passing towards a reflecting electrode I I where they are reflected and pass back through the grids It]. The device functions as stated above to generate self-maintained oscillations in known manner, the generated oscillations being fed from the resonator I, via a concentric line I2.

In order to tune the resonator I the upper wall I3 of said resonator is flexible and in order to deflect said wall thermal means in accordance with the invention are provided. As shown, a pair of expansible members I4 and I5 are provided in the form of bowed strips, each strip being carried by one of two rigid rectangular supports IS, IT, said supports I6 and I! being interconnected at their ends by brackets I8 and I9. The bowed strips i4 and I5 are welded or otherwise suitably secured at their ends to said supports I6 and I l, the latter being provided with longitudinal slots and -2I. The strip 54 is connected to a rod 22 which at its upper end is attached to a rigid disc 23 carried at the upper end of the support rods 5. The strip I5 is connected to a rod 24 which in turn is connected to a sleeve 25 attached to the flexible Wall I3 of the resonator I, the sleeve '25 also forming a support for the reflecting electrode II which is carried by an insulating disc 26. A plan view of strip I4 and support I6 is shown in Fig. 1a, strip I5 and support I1 being identical in construction save that member 24 is affixed below strip I5 and passes through slot 20. The strips I4 and I5 have substantially the same curvature and are disposed in registry so that the distance between them parallel to the rods 22 and 24 is substantially the same throughout their lengths. Each strip is arranged to be individually heated and in the embodiment of the invention shown in Figure 1 heating is effected by bombarding said strips with electrons which emanate from an elongated cathode 27 disposed, as shown, between said strips I4 and I5, the electron emission from the surface of the cathode 2'! opposite each strip I4 and I5 being controlled individually by control electrodes 23 and 29.

It will be observed from the construction shown in Fig. 1 that when the strip I5 is heated and it expands, the strip will bow further tending to move the wall I3 upwardly and when the strip I4 is heated it likewise expands and bows further causing the wall I3 to move downwardly. Providing the strips I4 and I5 are raised to substantially the same temperature no change in the position of the wall I3 will occur so that the position of this wall when the strips I4 and I5 are cold is substantially the same as its mean operating position when the strips I4 and I5 are equally heated, but as soon as differential heating of the strips I4 and I5 occurs then movement will be imparted to the wall I3 depending on the manner of the differential heating. In operating the device shown in the drawing the resonator I will usually be maintained at a positive potential which potential will be communicated to the strips I4 and I5 since all the parts are metallic and are not insulated from one another so'that the strips will collect the bombarding electrons from the cathode 27. If the strips I4 and I5 are not electrically connected to the resonator I, then separate leads will be required whereby the strips I4 and I5 can be maintained at appropriate operating potentials. To control the degree of the heating of each strip I4 and I5, the potentials applied in operation to the control electrodes 28 and 29 are varied, so controlling the electron emission and thus the degree of bombardment of the strips I4 and I5.

By means of the invention, movement of the wall I3 can be effected by differentially heating strips I4 and I5 thus obviating the disadvantage mentioned above in which movement of the element requiring adjustment in one direction was effected as a result of cooling.

The construction of the device shown in the drawing is particularly suitable for use in automatic frequency control, the proper frequency being obtained by suitably biassing the control electrodes 28 and 29, the bias potentials being then automatically controlled from the outputsof a push-pull pair of electron discharge devices. Alternatively, the bias potentials may be applied to the control electrodes 28 and 29 intermittently, the rate at which the potentials are applied being controlled in order to adjust the tuning of the resonator I.

The invention is not limited to the actual construction shown in the drawing, since instead of employing a pair of bowed strips I4 and I5, it is possible to employ other constructions. For example, as shown in Figure 2 of the drawings, the rod 24 is connected to one end of a rigid bar 5 3 0 to the other end of which there is connected at right angles thereto a pair of spaced parallel expansible members 3| and 32 mounted on a rigid support 33 and which are arranged to be differentially heated. When one of the members '3! or 32 is heated the-bar 30 tendsto pivot about the end ofthe other member andwhen the latter member is heated the bar 30 tends to pivot about the first member, the resultant movement of the opposite end of said' bar 30 being imparted to the rod24. The arrangement shown in Figure 2 is not so advantageous as that shown in Figure. 1

since it .will be appreciated :from Figure 2 that when-both 'of the rods 3| and 32 are heated,

movement of the rod 24 will occur, whereas with the arrangementshown inFigure 1 no movement of the rod 24 occurs until the strips I4. and 15 are difierentially heated. It is not necessary .to

heat the expansible members l4, l5 or'3l, 32

by bombarding them with electrons since other heating means may beused. For example, as

shown inFigure 2, each expansible member 3|, 32

is associated with a suitable form of heating coil 34, 35. application'to electron discharge devices em- Dloying hollow resonatorssince it canbe employed in connection with any other electrical device arranged in an envelope and having an elementthe position of which it is'reduired to adjust. Furthermore, the invention canalso be applied to electron discharge devices employing hollow resonators in which tuning of the latter is effected by the provision of :one or more plungers. If des'ired by suitable design bi-metallic strips may be employed. for the expansible 1 memberswivhich bi-metallio stripswill be arranged in the same manner as strips M and I5 shown in Fig. 1. I I

What I claim is:

1. An electron discharge devicecomprising a hollow resonator having a flexible wall whose position determines the tuning of said resonator, tuning means for said resonator comprising two metallic expansible members spaced equidistantly from each other, means mounted adjacent said expansible members for individually heating said members, a rigid link between said expansible members, another rigid link between the flexible wall of said resonator and one of said expansible members, and a sealed envelope surrounding said resjonaton'said tuning means, said heating means and saidrigid links. i a j j 2. An electron discharge device comprising a hollow resonator having a flexible wall-f'whose position determines the tuningof said resonator,

tuning means for said resonator comprising two metallic expansible members spaced equidistantly from each other, said expansible members comprising coextensively arranged metallic strips which are bowed in the same direction and have the same curvature, as a result of which the distance between them is substantially the same throughout their lengths, means mounted in heat conducting relationship to said expansible members for individually heating said members, a rigid link between said expansible members, another rigid link between the flexible wall of said resonator and one of said expansible members,

The invention is not limited-in its oscillatory circuit. having tuning means, said tun- -;.,.5. .An electron discharge device comprising a .ing means including a pair of metallic members spaced-equidistantly from each other and adapted Ito expand upon the-application of heat thereto, a.-cathode' located between said expansible mem bers for bombarding said members with electrons, ;a control electrode between each expansible memmberand said cathode for controlling the flow of electrons therebetween, a mechanical linkage between said metallic members, and a couplinglink -mountedbetween one .of saidmetallic members and "saidoscillatory circuit.

hollow-resonator having a flexible wall, a pair of similarly. bowed .and coextensive metallic expansible strips spaced equidistantly from each other, said strips having the same curvature and --being bowed in the same direction, a rigid link ymfrom the center of one strip to said flexible wall, l .and a rigid link from the center of the other strip .to a stationary support, said rigid links being oppositely disposed with respect to said expansible strips, means rigidly connecting said strips to each other, and means for differentially heating saidstrips. v

6. .An electron discharge devicecomprising a hollowresonator having a flexible wall, a pair 'oflsimilarly-bowed and coextensive metallic expansible strips and spaced equidistantly from each other, said 'stripsi having the same curvature and being bowed in the same direction, a

rigid link from the center of one, strip to said flexible wall, and a rigid link from the center of the other strip to a stationary support, said rigid links being oppositely disposed with respect to said expansible strips, means rigidly connecting said strips to each other, and means for-difrferentialiy heating said strips, said last means I including a cathode positioned between said strips -forbombarding the same with electrons and a controlrelectrode between each strip andsaid cathode for controlling the-electronflow therebetween, and a, sealed envelope enclosing said resonator, said strips,'said rigid links and said heating means. 7

7. In combination, a sealed envelope, an electrical device entirely enclosed within said sealed envelope, comprising a supporting structure sealed into a wall portion of said envelope, a

- resonator having fixed and adjustable elements,

a fixed element of said resonator being mounted on said supporting structure, a pair of thermally expansible members equidistantly spaced from 1 each other, one of said members being linked to and a sealed envelope surrounding said resonator.

said tuning means, said heating means and said rigid links.

3. An electron discharge device comprising a hollowresonator having a flexible wall whose position determines the tuning of said resonator, 75

tuning means for said resonator comprising two i f-the adjustable element of said resonator, and

means interposed between said expansible memsaid supporting structure, a rigid link mounted between said members. a further rigid link mounted between the other of said members and bers to individually heat said members.

8. An electron discharge device comprising a supporting member, a cavity resonator having thermally expansible members twoportions mutually adjustable with respect to each other, one of said portions of said resonator being mounted on said supporting member, tuning means for said resonator comprising two thermally expansible members equidistantly spaced from each other, one of said members being linked to said supporting member and the other of said members beinglinked to the remaining portion of said resonator, rigid mechanical links mounted between the ends of said expansible members, a cathode-arranged between said expansible members to bombard the same withelectrons and control electrodesarranged between said cathode and said expansible members to control the flow of electrons therebetween, and a sealed envelope surrounding said cavity resonator and said tuning means, said supporting member being sealed into a wall portion of said envelope.

9. An electron discharge device comprising a supporting member, a cavity resonator having two portions mutually adjustable with respectto each other, one of said portions of said resonator being mounted on said supporting member, tuning means for said resonator. comprising two equidistantly spaced from each other, one of said members being linked to said supporting member and the other of said members being linked to the remaining portion of said resonator, rigid mechanical links mounted between the ends of said expansible members, a cathode arranged between said expansible members to bombard the same with electrons and control electrodes arranged between said cathode and said expansible members to control the flow of electrons therebetween, and a sealed envelope surrounding said cavity resonator and said tuningmeans, said supporting member being sealed into a wall portion of said envelope and being separated into a plurality of conducting portions to conduct electric currents into the interior of said envelope to said resonator and said tuning means.

10. In combination, a sealed envelope and an electrical device enclosed within said envelope; said device including a rigid support and an'element requiring adjustment, means adjustably mounting said element comprising two thermallyexpansible members equidistantly spaced from each other, rigid means connecting said members, rigid means connecting said support to one of said members, rigid means connecting said element to the other member, and means for individually heating said members-said members being adapted to expand in the same direction when heated, whereby the adjustment of said element in either direction may be effected .by

differentially heating said expansible members, said two thermally-expansible members and said three rigid means constituting the sole means for maintaining said element in a particular adjusted position relative to said support.

11. Anfelectrical device including a rigid support, an element requiring adjustment movably mounted relative to said support. and means for efl'ecting adjustment of said element comprising two thermally-expansible members, means coupling parts of said members to each other, means rigidly coupling another part of one of said members to said support, .means rigidly coupling another part'of the other of said members to said element, and means for individually heating said members, said members being adapted to expand in the same direction when heated, whereby the adjustment of said element in either direction may be effected upon differentially heating said expansible :members, said two thermallyexpansible members and said three coupling means constituting the sole means for maintaining said element in a particular adjusted position relative to said support.

12. iAn' electrical device comprising a rigid support, an element requiring adjustment, and means 'adjustably mounting said element relative to said supportcomprising a pair of coextensive metallic expansible strips equidistantly spaced from each other, said strips having the same curvature and being bowed in the same direction, a rigid link from the center of one strip to said element, and a rigid link from the center of the other strip to said support, said rigid links being oppositely disposed with respect to said expansible strips, means rigidly connecting the adjacent ends of said strips to each other, and means for separately heating said strips.

ALBERT HORACE ATHERTON.

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